Solidity新手编写闪电贷合约遇Remix语法错误，求排查

错误信息 #

contracts/flash.sol:8:1: ParserError: Expected pragma, import directive or contract/interface/library/struct/enum definition.
address private wallet = 0x7e31a8ba5cF188fd39f9aaCF667E9dFE2311A882;
^-----^

问题代码 #

pragma solidity ^0.6.0;

import "https://github.com/aave/aave-solidity/contracts/AAVE.sol";
import "https://github.com/Uniswap/uniswap-v2-core/contracts/interfaces/IUniswapV2Pair.sol";
import "https://github.com/sushiswap/sushiswap-v2-core/contracts/interfaces/ISushiV2Pair.sol";

// Set the wallet address
address private wallet = 0x0000000000000000000000000;

// Set the contract addresses
address private aave = 0x7deB5e830be29F91E298ba5FF1356BB7fC8B8C9D; // AAVE contract address
address private uniswap = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f; // Uniswap contract address
address private sushiswap = 0x6b3595068778dd592e39a122f4f5a5cf09c90fe2; // SushiSwap contract address

// Set the token addresses
address private eth = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE; // ETH token address
address private ape = 0x27Dce1e12396F3a2B49E4FdD7a4C9d938E5e5F97; // APE token address

// Set the contract ABIs
AAVE aaveContract;
IUniswapV2Pair uniswapContract;
ISushiV2Pair sushiswapContract;

constructor() public {
    aaveContract = AAVE(aave);
    uniswapContract = IUniswapV2Pair(uniswap);
    sushiswapContract = ISushiV2Pair(sushiswap);
}

// Borrow 100 ETH from AAVE
function borrowFromAAVE() public {
    aaveContract.borrow(eth, 100 ether, wallet);
}

// Swap 20 ETH to APE on SushiSwap
function swapETHtoAPEonSushiSwap(uint amount) public {
    sushiswapContract.swap(amount ether, 10**18, ape, wallet, address(this));
}

// Swap 80 ETH to APE on Uniswap
function swapETHtoAPEonUniswap(uint amount) public {
    uniswapContract.swapETHForExactTokens(amount ether, 10**18, ape, wallet, address(this));
}

// Swap all APE to ETH on SushiSwap
function swapAPEtoETHonSushiSwap(uint amount) public {
    sushiswapContract.swap(amount, 10**18, eth, wallet, address(this));
}

// Pay back the loan to AAVE
function payBackLoanToAAVE() public {
    // First, check if the wallet has sufficient balance to pay back the loan
    require(wallet.balance >= aaveContract.borrowBalance(eth, wallet), "Insufficient balance to pay back the loan.");

    // Pay back the loan
    aaveContract.repayBorrow(eth, wallet);
}

// Keep the profit in the wallet
function keepProfitInWallet(uint amount) public {
    // First, check if the contract has sufficient balance to transfer the profit to the wallet
    require(address(this).balance >= amount, "Insufficient balance in the contract.");

    // Transfer the profit to the wallet
    wallet.transfer(amount);
}

问题根源 #

Solidity语法要求所有状态变量、函数、构造函数等必须定义在contract、interface或library代码块内部，不能直接写在全局作用域（pragma和import语句之后直接声明变量/函数）。你的代码中，wallet、aave等变量以及构造函数、各种函数都直接暴露在全局，违反了Solidity的结构规范，导致解析器报错。

修复方案 #

将所有变量、构造函数和函数包裹在一个contract代码块内，修改后的代码如下：

pragma solidity ^0.6.0;

import "https://github.com/aave/aave-solidity/contracts/AAVE.sol";
import "https://github.com/Uniswap/uniswap-v2-core/contracts/interfaces/IUniswapV2Pair.sol";
import "https://github.com/sushiswap/sushiswap-v2-core/contracts/interfaces/ISushiV2Pair.sol";

// 核心修改：添加contract代码块包裹所有内容
contract FlashLoanArbitrage {
    // Set the wallet address
    address private wallet = 0x0000000000000000000000000;

    // Set the contract addresses
    address private aave = 0x7deB5e830be29F91E298ba5FF1356BB7fC8B8C9D; // AAVE contract address
    address private uniswap = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f; // Uniswap contract address
    address private sushiswap = 0x6b3595068778dd592e39a122f4f5a5cf09c90fe2; // SushiSwap contract address

    // Set the token addresses
    address private eth = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE; // ETH token address
    address private ape = 0x27Dce1e12396F3a2B49E4FdD7a4C9d938E5e5F97; // APE token address

    // Set the contract ABIs
    AAVE aaveContract;
    IUniswapV2Pair uniswapContract;
    ISushiV2Pair sushiswapContract;

    constructor() public {
        aaveContract = AAVE(aave);
        uniswapContract = IUniswapV2Pair(uniswap);
        sushiswapContract = ISushiV2Pair(sushiswap);
    }

    // Borrow 100 ETH from AAVE
    function borrowFromAAVE() public {
        aaveContract.borrow(eth, 100 ether, wallet);
    }

    // Swap 20 ETH to APE on SushiSwap
    function swapETHtoAPEonSushiSwap(uint amount) public {
        sushiswapContract.swap(amount ether, 10**18, ape, wallet, address(this));
    }

    // Swap 80 ETH to APE on Uniswap
    function swapETHtoAPEonUniswap(uint amount) public {
        uniswapContract.swapETHForExactTokens(amount ether, 10**18, ape, wallet, address(this));
    }

    // Swap all APE to ETH on SushiSwap
    function swapAPEtoETHonSushiSwap(uint amount) public {
        sushiswapContract.swap(amount, 10**18, eth, wallet, address(this));
    }

    // Pay back the loan to AAVE
    function payBackLoanToAAVE() public {
        // First, check if the wallet has sufficient balance to pay back the loan
        require(wallet.balance >= aaveContract.borrowBalance(eth, wallet), "Insufficient balance to pay back the loan.");

        // Pay back the loan
        aaveContract.repayBorrow(eth, wallet);
    }

    // Keep the profit in the wallet
    function keepProfitInWallet(uint amount) public {
        // First, check if the contract has sufficient balance to transfer the profit to the wallet
        require(address(this).balance >= amount, "Insufficient balance in the contract.");

        // Transfer the profit to the wallet
        wallet.transfer(amount);
    }
}

额外提示 #

• 注意swapETHForExactTokens等函数的参数是否符合对应接口的定义，Uniswap V2的swapETHForExactTokens参数顺序和你的代码可能存在差异，后续测试时需要核对接口文档。
• 闪电贷的核心逻辑需要确保在同一个交易内完成借贷、套利、还款流程，当前代码的函数是分散的，需要整合为单一的闪电贷执行函数，否则无法完成闭环。

内容的提问来源于stack exchange，提问作者Alex